1. Field of the Invention
The present invention relates generally to disposable garments such as diapers and incontinent pad type garments More particularly, the present invention relates to an improvement in the composition of adhesives used to bond nonwoven material and an impermeable film in such garments. Further, the present invention relates to a method for producing such improved garments.
2. Description of the Related Art
Disposable garments such as diapers and incontinent pad type garments usually comprise a moisture impermeable outer film, an intermediate absorbent pad and a moisture permeable inner liner commonly called "nonwoven" material. Disposable garments are typically bonded together utilizing a hot melt adhesive either extruded or sprayed onto the film and/or nonwoven material. This conventional product and assembly method suffers from a number of shortcomings.
Adhesives presently used for bonding garments together include those generally referred to as pressure and semi-pressure sensitive adhesives. Examples of polymers used in present adhesive compositions are styrene-isoprene-styrene, styrene-butadiene-styrene, amorphous polypropylene and ethylene vinyl acetate. These polymers are blended with any of a variety of tackifying resins to impart tack to the hot melt at room temperature. Additional additives are used to modify viscosity and give heat stability.
The adhesive is either extruded in multiline form or sprayed onto the impermeable film. In either case, direct application on the garment production line is labor intensive. Monitoring and close control of application conditions are needed to assure adequate product quality and quantity. Approximately 0.9 gram to 1.5 grams of adhesive is required per garment in order to bond the impermeable film to the nonwoven backing.
Hot melt adhesives have undesirable characteristics when used in connection with these products. Such adhesives are solid at room temperature and become thermoplastic when heated for application. While hot melt pressure and semi-pressure sensitive adhesives effectively bond garments when correctly applied, they do have negative consequences to production, quality and cost of the disposable product. The film to which the high temperature thermoplastic material is applied can be distorted by the elevated temperature. Likewise, a cooling period is required after application and bonding of the film and nonwoven material. Furthermore, the application of multiple beads of melted adhesive in a high speed production line complicates the manufacture and maintenance of high quality standards and, as a result, the ultimate quality of the finished product.
An improvement in the adhesive composition which would avoid the above-mentioned problems and could be used in a high speed, efficient manufacturing system, would prove to be a significant advancement in the art.
FIG. 1 is provided to illustrate a schematic of a conventional prior art system for producing disposable garments. In FIG. 1, a roll 20 supplies a moisture impermeable web or film 22 to produce garments. The garments also comprise an interliner web of absorbent or permeable nonwoven material 24 and individual absorbent pads 26. The film or web 22, the web of nonwoven material 24 and absorbent pads 26 move in a direction indicated by arrows 28. An adhesive applicator station 30 includes one or more nozzles 32 for applying the adhesive to the film 22. After application of the adhesive, the material's are pressure bonded together by means of nip rolls 34, and thereafter separated into individual garments by means of a conventional slitting and/or transverse cutting operation (not shown).
FIGS. 2A and 2B are also prior art illustrations showing alternative methods conventionally used to apply adhesive. In FIG. 2A, a number of extrusion nozzles 32A apply individual beads of adhesive onto the film 22. Similarly, in FIG. 2B, individual spray nozzles 32B spray a swirl pattern on the film prior to bonding.
Clogging, slow line speed and control of adhesive quantity all present problems in the operation of these earlier systems. A system for producing disposable garments which would avoid the above-mentioned problems and could be used in a high speed efficient manufacturing system, would prove to be a significant advancement in the art.